1. Field of the Invention
The present invention relates to a scroll compressor to be used in an air conditioner, etc., more specifically, a scroll compressor having an Oldham's ring to demonstrate the gas compression function by suppressing the rotation of an orbiting scroll, and performing the smooth turning motion relative to a fixed scroll.
2. Description of the Related Art
In a scroll compressor with the characteristics of low vibration and low noise to be used in an air conditioner for home use, etc., as indicated in FIG. 1 of Japanese Unexamined Patent Publication No. 64-32092 Official Gazette, an orbiting scroll comprising a disk-shaped end plate and a spiral wrap which is integratedly formed on the end plate in an upright manner is engaged with a fixed scroll with similar constitution to that of the orbiting scroll and having a discharge port at the center of the end plate so that side walls of the wraps are brought into contact with each other, both scrolls are stored in a cylindrical sealed container having a suction port, the fixed scroll is fixed to the sealed container, the rotation of the orbiting scroll is prevented by a rotation preventive device, a crank shaft having an eccentric part fitted to the orbiting scroll is turned by driving a motor to drive the orbiting scroll so that the center of the spiral of the wrap of the orbiting scroll is turned around the center of the spiral of the wrap of the fixed scroll while the wraps of both scrolls are kept in a contact condition.
FIG. 4 schematically shows a compression mechanism part of a well-known scroll compressor, and its structure is described in detail.
Referring to FIG. 4, the scroll compressor has a compression mechanism part 20, an orbiting scroll 21, a boss part 21a, a bearing 21b, a wrap 21c, a key groove 21d, a fixed scroll 22, a wrap 22a, a flange part 22b, a frame 23, a main bearing part 23a, a key groove 23b, a flange part 23c, a screw hole 23d, a bolt 24, a crank shaft 25, an eccentric part 25a, an Oldham's ring 26, an Oldham's key 26a, an annular part 26b of the Oldham's ring, a motor 27, a rotor 27a, a stator 27b, and a sealed container 28.
That is, FIG. 4 is an elevational sectional view of a well-known typical scroll compressor, and in the compression mechanism part 20, the stator 27a of the motor 27 is fitted through press-fitting, etc., to a lower end side of the crank shaft 25 inserted in the main bearing part 23a of the frame 23 as mentioned above, the bearing 21b provided on the boss part 21a of the orbiting scroll 21 is fitted to the eccentric part 25a of the crank shaft 25, the fixed scroll 22 whose wrap 22a is brought into contact and engaged with the wrap 21c of the orbiting scroll 21 is arranged as illustrated in the figure, and further, as shown in FIG. 5, the projected Oldham's key 26a which is orthogonally arranged in an integrated manner with upper and lower surfaces of the annular part 26b having an arbitrary thickness which is the rotation preventive mechanism of the orbiting scroll 21 is engaged with the key groove 21d of the orbiting scroll 21 and the key groove 23b of the frame 23 respectively to prevent the rotation of the orbiting scroll 21, a plurality of bolts 24 are inserted in through holes 22c provided in the flange part 22b of the fixed scroll 22, and screwed in the screw holes 23d provided in the flange part 23c of the frame 23, and the wraps 21c, 22a are regulated in alignment and tightened to complete the assembly of the compression mechanism part 20.
The stator 27b of the motor 27 is welded at an arbitrary position of a lower part of the sealed container 28, and the frame 23 of the sealed container 28 and the compression mechanism part 20 is locked through a plurality of spot welding between the inside diameter of the stator 27b and the outside diameter of the rotor 27a which is pre-welded to the crank shaft 25 of the compression mechanism part 20 while keeping an appropriate air gap.
In such a scroll compressor, the quantity of unbalance caused by the rotation for the orbiting scroll 21, the crank shaft 25 and the rotor 27a of the motor 27 can be eliminated by reducing the weight thereof through appropriate spot facing, or by adding a balance weight thereto.
However, only the Oldham's ring 26, in which its Oldham's key 26a is inserted in the key grooves 21d, 23b of the orbiting scroll 21 and the frame 23 respectively to prevent the rotation of the orbiting scroll 21, and the rotational motion of the eccentric part 25a of the crank shaft 25 is converted into the oscillating motion of the orbiting scroll 21 in order to prevent the rotation of the orbiting scroll 21, is reciprocated to generate the vibration attributable to its weight. In particular, the noise caused by the resonance, etc., of each part raises a problem in a room air conditioner for home use, etc., in which the high-speed rotation is required in the inverter control, etc.
Further, in such a well-known scroll compressor, a ferrous Oldham's ring is often used in order to improve the reliability in slidability between the Oldham's key 26a and the key grooves 21d, 23b, and the vibration is increased as the weight is increased compared with the Oldham's ring consisting of the light metal such as aluminum, with the result against the low-vibration and low-noise properties which are the original object for the scroll compressor.